Plant oil is a valuable renewable resource. Plant lipids have a variety of industrial and nutritional uses and are central to plant membrane function and climatic adaptation. Besides the nutritional uses, vegetable oils are gaining increasing interest as substitutes for petroleum-derived materials in fuels, lubricants, and specialty chemicals, especially as crude oil supplies decline. Oilseeds provide a unique platform for the production of high-value fatty acids that can replace non-sustainable petroleum products. (Cahoon et al. (2007) Curr. Opin. Plant Biol. 10:236-244). Methods to increase the content and to improve and alter the composition of plant oils are therefore desired.
Triacylglycerol (TAG) is the primary component of vegetable oil in plants; it is used by the seed as a stored form of energy to be used during seed germination. The quality and content of plant oil can be altered by various methods, by impinging on the enzymes involved directly or indirectly in TAG biosynthesis.
There are limitations to using conventional plant breeding to alter fatty acid composition and content. Molecular and cellular biology techniques offer the potential for overcoming some of the limitations of the conventional breeding approach. Some of the particularly useful technologies are seed-specific expression of foreign genes in transgenic plants (Goldberg et al. (1989) Cell 56:149-160), and the use of antisense RNA to inhibit plant target genes in a dominant and tissue-specific manner (van der Krol et al. (1988) Gene 72:45-50]. Other advances include the transfer of foreign genes into elite commercial varieties of commercial oilseed crops, such as soybean (Chee et al. (1989) Plant Physiol. 91:1212-1218; Christou et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86:7500-7504; Hinchee et al. (1988) Bio/Technology 6:915-922; EPO publication 0 301 749 A2], rapeseed (De Block et al. (1989) Plant Physiol. 91:694-701), and sunflower (Everett et al. (1987) Bio/Technology 5:1201-1204), and the use of genes as restriction fragment length polymorphism (RFLP) markers in a breeding program, which makes introgression of recessive traits into elite lines rapid and less expensive (Tanksley et al. (1989) Bio/Technology 7:257-264). However, application of each of these technologies requires identification and isolation of commercially-important genes.
Transcription factors regulate transcription and orchestrate gene expression in plants and other organisms; control of transcription factor gene expression provides a powerful means for altering plant phenotype. The transformation of plants with transcription factors, however, can result in aberrant development based on the overexpression and/or ectopic expression of the transcription factor, and thus, tight control of timing, strength and location of transcription factor expression is crucial for optimal phenotype. Using strong seed-specific promoters or strong constitutive promoters can lead to aberrant phenotypes.